READ IT RIGHT
How many digits do you estimate when reading ANY analog tool?
Exactly ONE — the last digit
How many sig figs in 500?
One
1 mole = how many particles, and where is that printed?
6.02×10²³
on the back of your periodic table sheet
Say the density formula, and where can you always find it?
D = m ÷ V
It's printed on the periodic table formula sheet
On a lab day, goggles come off only when…
EVERY group is finished with glass, chemicals, and fire
1 mole = how many particles, and where is that printed?
6.02×10²³
on the back of your periodic table sheet
How many sig figs in 0.003090?
Four
Write 0.0000356 in scientific notation.
3.56×10⁻⁵
m = 25.0 g and V = 10.0 mL. Density?
2.50 g/mL
Acid spill on the bench — neutralize it with what?
A weak base: baking soda (then wipe it up)
A cylinder has a line for every 1 mL. Your reading must go to which place?
The TENTHS place (estimate one digit past the lines)
Round 0.0030955 to three sig figs.
0.00310 (the trailing zero must stay)
Convert 250,000 cL to L.
2,500 L (100 cL = 1 L)
Accuracy vs. precision:
one sentence each.
Accuracy = close to the TRUE value.
Precision = close to EACH OTHER.
Name the porcelain vessel used to heat small amounts.
The crucible
Before: 25.0 mL. After the rock goes in: 36.5 mL. The rock's volume?
11.5 mL (after − before)
5.221 m + 4.30 m = ?
9.52 m (fewest DECIMAL places)
What equality can you make from 55.0 miles/hr?
55.0 miles = 1 hour
Measured 4.55 g/mL; actual 4.95 g/mL. Percent error?
8.08% (0.40 ÷ 4.95 × 100)
Fire blanket vs. fire extinguisher
which is for what?
Blanket = a PERSON on fire.
Extinguisher = a fire at the station.
45.5 g of NH₃ (molar mass 17.04). How many molecules?
1.61×10²⁴ (÷17.04 → moles, × 6.02×10²³)
4310 × 0.593 × 75 = ?
1.9×10⁵ (75 has only 2 sig figs)
Convert 621 cg to ng.
6.21×10⁹ ng (through grams: 6.21 g, then ×10⁹)
Osmium: D = 22.57 g/mL. Mass of a 12.5-mL block?
282 g (12.5 × 22.57 = 282.125 → 3 sig figs)
Which tool delivers precise volumes, especially in titrations?
The burette